Palladium and palladium alloys are extensively used in a variety of industrial applications including the fabrication of jewelry, optical devices, and electronic circuits and devices. Palladium and its alloys are attractive because of chemical inertness, surface luster, high electrical conductivity, and excellent surface properties, particularly for electrical contacts. In many applications, chemical inertness is highly advantageous for long life and high reliability. This is particularly true for applications in electrical and electronic devices.
Because of chemical inertness and reasonable surface hardness, palladium is especially attractive as an electrical contact material in electrical connectors, relay contacts, switches, etc. Various palladium alloys such as palladium silver are also useful for the same applications. Indeed, because of the increasing cost of gold, palladium becomes more and more attractive economically as a contact material, surface material, and in other applications. In many applications where gold is used, it is often economically attractive to use palladium, provided an inexpensive and efficient method of plating ductile and adherent palladium is available.
Highly desirable is a process for plating palladium from an aqueous solution which is highly reliable despite the possible introduction of foreign ions into the bath which might adversely affect the plating process. This is most critical in plating various types of electrical connectors (switches, relays, etc.) and other electrical devices because of the possibility of introducing copper ions into the plating bath.
Palladium electroplating processes and baths have been described in a number of references including U.S. Pat. No. 1,970,950, issued to E. M. Wise on Aug. 21, 1934 and U.S. Pat. No. 1,993,623, issued to A. R. Raper on Mar. 5, 1935.